Multiple unit backwashing gravity flow filter

Claim 1

A MULTIPLE UNIT GRAVITY BACKWASHING FILTER COMPRISING A FILTERED WATER RESERVOIR HAVING A PLURALITY OF SEPARATE INLET PORTS FOR FILTERED LIQUID AND A COMMON OUTLET CONTROLLED BY AN OUTLET WEIR FOR MAINTAINING A CONSTANT PREDETERMINED LEVEL OF LIQUID IN SAID RESERVOIR AND FOR PERMITTING THE ESCAPE OF EXCESS LIQUID AT ALL TIMES FROM THE RESERVOIR, A BACKWASH EFFLUENT LIQUID CHAMBER SUPPORTED ON AND ABOVE SAID RESERVOIR, A MULTIPLICITY OF RELATIVELY ISOLATED FILTER UNITS SURROUNDING SAID RESERVOIR, EACH SAID UNIT COMPRISING A HORIZONTAL FILTER BED, SAID RESERVOIR PORTS COMMUNICATING WITH THE RESPECTIVE SAID UNITS AT A LEVEL BENEATH THE FILTER BEDS THEREOF AND BEING OPEN TO PERMIT FREE BI-DIRECTIONAL FLOW OF LIQUID THERETHROUGH BOTH INTO AND FROM THE RESERVOIR SOLELY IN ACCORDANCE WITH CHANGES IN THE LEVELS OF LIQUID IN THE RESPECTIVE UNITS, IN COMBINATION WITH INFLUENT SUPPLY MEANS NORMALLY DELIVERING INFLUENT LIQUID TO SAID UNITS ABOVE THEIR RESPECTIVE FLITER BEDS AT A SUFFICIENT RATE TO MAINTAIN THE LEVEL OF LIQUID OVER SAID BEDS APPRECIABLY HIGHER THAN SAID LEVEL OF LIQUID IN THE RESERVOIR, AND SELECTIVELY CONTROLLABLE MEANS INCLUDING FLUID CONDUITS COMMUNICATING WITH SAID CHAMBER AND WITH EACH OF SAID UNITS AT A LEVEL LIQUID WITHIN THE TIVE FILTER BEDS AND BELOW THE SAID LIQUID LEVEL WITHIN THE RESERVOIR FOR WITHDRAWING LIQUID FROM ABOVE THE FILTER BED OF A GIVEN UNIT TO A LEVEL BELOW SAID PRE-DETERMINED LEVEL WITHIN THE RESERVOIR TO ESTABLISH A GRAVITY BACKWASHING FLOW OF LIQUID FROM THE RESERVOIR UPWARDLY THROUGH THE BED OF SAID UNIT ONLY, WHILE PERMITTING THE REMAINING UNITS TO SUPPLY LIQUID TO SAID RESERVOIR AND ALSO TO REMOVE BACKWASH EFFLUENT LIQUID FROM SAID GIVEN UNIT.